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Glaciation in Alaska

Description: From introduction: The history of glaciation in Alaska offers a fascinating field for study. Because of the remarkable development and easy accessibility of valley and piedmont glaciers in the coastal mountains, Alaska has long been popularly conceived as a land of ice and snow, a concept that is only slowly being corrected. To the student of glaciation, however, Alaska affords a unique opportunity to observe the formation, movement, and dissipation of the many living glaciers, to examine the results of glacial erosion on a gigantic scale, and to discover and work out the sequence of Pleistocene events as shown by the topographic forms in both glaciated and unglaciated areas and by the deposits left by ice and water during earlier stages of glaciation.
Date: 1931
Creator: Capps, Stephen R.
Partner: UNT Libraries Government Documents Department

On the detection of crevasses in glacial ice with synthetic-aperture radar.

Description: The intent of this study is to provide an analysis of the scattering from a crevasse in Antarctic ice, utilizing a physics-based model for the scattering process. Of primary interest is a crevasse covered with a snow bridge, which makes the crevasse undetectable in visible-light images. It is demonstrated that a crevasse covered with a snow bridge can be visible in synthetic-aperture-radar (SAR) images. The model of the crevasse and snow bridge incorporates a complex dielectric permittivity model for dry snow and ice that takes into account the density profile of the glacier. The surface structure is based on a fractal model that can produce sastrugi-like features found on the surface of Antarctic glaciers. Simulated phase histories, computed with the Shooting and Bouncing Ray (SBR) method, are processed into SAR images. The viability of the SBR method for predicting scattering from a crevasse covered with a snow bridge is demonstrated. Some suggestions for improving the model are given.
Date: February 1, 2010
Creator: Brock, Billy C.
Partner: UNT Libraries Government Documents Department

Retreating Glaciers of the Himalayas: A Case Study of Gangotri Glacier Using 1990-2009 Satellite Images

Description: This paper discusses research on the spatial and temporal variation of the Gangotri Glacier, one of the largest glaciers in the Himalayas. The authors discuss how this influences the River Ganges and, consequently, the people of the Indian subcontinent.
Date: April 1, 2010
Creator: Ding, Jennifer & Dong, Pinliang
Partner: UNT Honors College

Laurentide Ice Sheet meltwater and abrupt climate change during the last glaciation

Description: A leading hypothesis to explain abrupt climate change during the last glacial cycle calls on fluctuations in the margin of the North American Laurentide Ice Sheet (LIS), which may have routed freshwater between the Gulf of Mexico (GOM) and North Atlantic, affecting North Atlantic Deep Water (NADW) variability and regional climate. Paired measurements of {delta}O and Mg/Ca of foraminiferal calcite from GOM sediments reveal five episodes of LIS meltwater input from 28-45 thousand years ago (ka) that do not match the millennial-scale Dansgaard-Oeschger (D/O) warmings recorded in Greenland ice. We suggest that summer melting of the LIS may occur during Antarctic warming and likely contributed to sea-level variability during Marine Isotope Stage 3 (MIS 3).
Date: October 2, 2005
Creator: Hill, H W; Flower, B P; Quinn, T M; Hollander, D J & Guilderson, T P
Partner: UNT Libraries Government Documents Department

The use of predictive lithostratigraphy to significantly improve the ability to forecast reservoir and source rocks? Final CRADA report.

Description: The purpose of this CRADA, which ended in 2003, was to make reservoir and source rock distribution significantly more predictable by quantifying the fundamental controls on stratigraphic heterogeneity. To do this, the relationships among insolation, climate, sediment supply, glacioeustasy, and reservoir and source rock occurrence were investigated in detail. Work current at the inception of the CRADA had uncovered previously unrecognized associations among these processes and properties that produce a phenomenon that, when properly analyzed, will make lithostratigraphic variability (including texture, porosity, and permeability) substantially more understandable. Computer climate simulations of selected time periods, compared with the global distribution of paleoclimatic indicators, documented spatial and temporal climate changes as a function of insolation and provided quantitative changes in runoff, lake level, and glacioeustasy. The effect of elevation and climate on sediment yield was assessed numerically by analyzing digital terrain and climate data. The phase relationships of climate, yield, and glacioeustatic cycles from the Gulf of Mexico and/or other sedimentary basins were assessed by using lacunarity, a statistical technique.
Date: June 29, 2010
Creator: Doctor, R. D.; Moore, T. L. & Systems, Energy
Partner: UNT Libraries Government Documents Department

Holocene Paleohydrology of the tropical andes from lake records

Description: Two century-scale time series in northern Bolivia constrain the ages of abrupt changes in the physical, geochemical, and biological characteristics of sediments obtained from lakes that formed during deglaciation from the late Pleistocene glacial maximum. The watersheds of Laguna Viscachani (16{degrees}12`S, 68{degrees}07`W, 3780m) and Lago Taypi Chaka Kkota (16{degrees}13`S, 68{degrees}21`W, 4300m), located on the eastern and western slopes of the Cordillera Real, respectively, contain small cirque glaciers. A high-resolution chronology of the lake sediments is provided by 23 AMS {sup 14}C dates of discrete macro-fossils. Late Pleistocene glaciers retreated rapidly, exposing the lake basins between 10,700 and 9700 {sup 14}C yr B.P. The sedimentary facies suggest that after 8900 {sup 14}C B.P. glaciers were absent from the watersheds and remained so during the middle Holocene. An increase in the precipitation-evaporation balance is indicated above unconformities dated to about 2300 {sup 14}C yr B.P. in both Lago Taypi Chaka Kkota and Laguna Viscachani. An abrupt increase in sediment accumulation rated after 1400 {sup 14}C yr B.P. signals the onset of Neoglaciation. A possible link exists between the observed millennial-scale shifts in the regional precipitation- evaporation balance and seasonal shifts in tropical insolation.
Date: March 3, 1997
Creator: Abbott, M. B., LLNL
Partner: UNT Libraries Government Documents Department

Bryophyte-Cyanobacteria Associations during Primary Succession in Recently Deglaciated Areas of Tierra del Fuego (Chile)

Description: Article on bryophyte-cyanobacteria associations during primary succession in recently deglaciated areas of Tierra del Fuego (Chile).
Date: May 12, 2014
Creator: Arróniz-Crespo, María; Pérez-Ortega, Sergio; De Los Ríos, Asunción; Green, T. G. Allan; Ochoa-Hueso, Raúl; Casermeiro, Miguel Ángel et al.
Partner: UNT College of Arts and Sciences

EPA's Response to the Petitions to Reconsider the Endangerment and Cause or Contribute Findings for Greenhouse Gases under Section 202(a) of the Clean Air Act

Description: This set of volumes is a response by the EPA to ten petitions filed to challenge the determination that climate change is real. The EPA dismisses the petitioners' claims, reiterating the evidence of anthropogenic global climate change.
Date: July 29, 2010
Creator: United States. Environmental Protection Agency. Office of Atmospheric Programs. Climate Change Division.
Partner: UNT Libraries